Concentric multipactor



Feb. 21, 1939. R. 1.. $NYDER CONCENTRIC MULTIPACTOR Filed July 18, 1936 MIMI ii:

INVENTOR RICHARD L. SNYDER.

Patented Feb. 21, 1939 warren stares PATENT OFFICE CONCENTRIC MULTIPAGTOR Application July 18, 1936, Serial No. 91,343

3 Claims.

My invention relates to electron multipliers and more particularly to that type of electron multiplier wherein electrons are directed to successively impact a series of emitter elements to 5 produce a current augmented by secondary emission at each impact.

When a series of emitting elements are placed with relation to each other and maintained at successively increasing potentials so that elecl trons may be drawn from one to another until the entire series has been impacted, the degree of multiplication depends, among other things, upon providing electron paths offering a minimum limitation of flow thereof along such paths. 15 Among the objects of my invention are: to

provide an electron multiplier arranged to provide a high degree of multiplication; to provide a compact multiplier unit; to provide an arrangement and construction in an electron multiplier 20 whereby electrons themselves in the aggregate determine their own paths; and to provide a structural arrangement of an electron multiplier calculated to facilitate simplicity in manufacture.

Other objects of my invention will be apparent 25 or will be specifically pointed out in the description forming a part of this specification, but I do not limit myself to the embodiment of the invention herein described, as various forms may be adopted within the scope of the claims.

30 Referring to the drawing:

Figure 1 is a sectional view of an multiplier;

Figure 2 is a sectional view from line 2-2 of Figure 1; and

35 Figure 3 is a sectional view from line 33 of Figure 1.

In the preferred embodiment the electron multiplier comprises an evacuated cylindrical envelope I closed at both ends by end walls 2 40 and 3. Sealed through the central input stem 4 in end wall 2 are the leads 5 of the filamentary cathode 6 and the lead 'I for a control grid 8. Mounted as by lead 9 sealed in stem I0 in end Wall 3 with its surface normal to and with its 45 center preferably coincident with the axis of the envelope is a disk II. The surface Ila of disk II, which is disposed toward the cathode 6, is sensitized for secondary emission and may be sensitized for this purpose by having deposited 50 thereon a coating of thorium, caesium, or the like. Disk II is surrounded by a similarly sensitized flat ring I2 mounted in the same plane but spaced therefrom and providing a second secondarily emissive surface I2a, and being mount- 55 ed upon a lead in I3 sealed through stem I I]. A

electron pair of similarly shaped rings I4 and I5 are concentrically mounted with respect to each other and to surround grid 8, leads I6 and I1, respectively, being secured thereto and sealed through stem I8 for the purpose. The ring i4 is sensi- 5 tized for secondary emission. An open mesh accelerating anode 28 is provided midway of the tube and energized to a higher potential than any of the other electrodes by battery 29. This prevents electrons from going to an electrode of 10 higher potential on the same side of the tube.

Filament 6 is energized from a source I9 and electrons from the filament are accelerated by anode 28 toward the sensitized surface of disk II under control of grid 8. In order to provide necessary energization of emitter elements aresistor is connected across the potential source 2|, taps 22, 24, and 26 leading respectively to the cathode 6, and the emitter elements I I,

I4 and I2 to produce progressively increasing 20 potentials thereon, the end of the resistor being connected to the anode ring I5 through lead I! and an output impedance 21, the latter being so connected that variations in current therefrom may be utilized. 25

Energized as described above, electrons leaving the filament 6 pass through grid 8 and are accelerated to the first emitter element II a in the series and a larger number of secondary electrons are emitted therefrom. These secondary 30 electrons are draw-n across the tube to the second emitter element I la and cause the emission therefrom of a still larger number of electrons, these latter secondaries being drawn to the opposing emitter element I2a for the release therefrom' of a still further multiple of the impacting electrons. The electrons released from element I2a are drawn to anode I5 for utilization in the output impedance 21.

It will be observed that the respective areas 40 of the emitter elements Ila, Ma and I2a are preferably progressively greater and that this progression corresponds to the progressively increasing number of electrons which impact these surfaces. This arrangement tends to maintain electron densities in the space between successive elements within desirable limits, thus minimizing any tendency to create space charges. As indicated by the arrows in Figure 1, the successive paths of the emitted electrons tend outwardly of the tube axis and those in each path tend to cause those in the succeeding outer path to deflect outwardly, these tendencies being overcome by the potentials on the emitter elements. On the other hand, the preponderance of electrons moving in the outer spaces, as for instance in the space between the emitter l2a and anode I5, tend to maintain those in the inner interelement spaces directed toward the proper emitter elements.

It will be apparent that simplicity and compactness of this electron multiplier are coupled with the facts that the arrangement is inherenvelope, means for producing electrons therein, means therein capable of releasing electrons by secondary emission comprising a plurality of spaced groups of concentrically spaced elements, each group being in the same plane.

- 2. An electron multiplier comprising a cylindrical envelope, means providing spaced groups of concentrically related secondary emissive surfaces at the ends thereof, each group being in the same plane, and means for directing electrons against an inner surface to release secondary electrons therefrom.

3. An electron multiplier comprising an envelope, a series of concentrically mounted washerlike surfaces capable of emitting electrons by secondary emission therefrom, means for directing electrons serially against said surfaces to cause secondary emission therefrom, and means for collecting electrons emitted from the other surface.

RICHARD L. SNYDER. 

